Vapor-assisted engineering heterostructure of 1D Mo3N2 nanorod decorated with nitrogen-doped carbon for rapid pH-Universal hydrogen evolution reaction

Reasonable construction of heterostructure is of significance yet a great challenge towards efficient pH-universal catalysts for hydrogen evolution reaction (HER). Herein, a facial strategy coupling gas-phase nitridation with simultaneous heterogenization has been developed to synthesize heterostructure of one-dimensional (1D) Mo₃N₂ nanorod decorated with ultrathin nitrogen-doped carbon layer (Mo₃N₂@NC NR). Thereinto, the collaborative interface of Mo₃N₂ and NC is conducive to accomplish rapid electron transfer for reaction kinetics and weaken the Mo–H_ads bond for boosting the intrinsic activity of catalysts. As expected, Mo₃N₂@NC NR delivers an excellent catalytic activity for HER with low overpotentials of 85, 129, and 162 mV to achieve a current density of 10 mA cm^?2 in alkaline, acidic, and neutral electrolytes, respectively, and favorable long-term stability over a broad pH range. As for practical application in electrocatalytic water splitting (EWS) under alkaline, Mo₃N₂@NC NR || NiFe-LDH-based EWS also exhibits a low cell voltage of 1.55 V and favorable durability at a current density of 10 mA cm^?2, even surpassing the Pt/C || RuO₂-based EWS (1.60 V). Consequently, the proposed suitable methodology here may accelerate the development of Mo-based electrocatalysts in pH-universal non-noble metal materials for energy conversion.     

钛基表面PDLLA/ZnO纳米阵列材料的制备及生物学性能

采用水热生长法,在钛基表面制备高度有序、尺寸可控的氧化锌纳米棒阵列,再通过静电吸附的方法在其表面自组装一层具有良好生物相容性的聚乳酸生物涂层。利用SEM,MTT,LDH方法对细胞形态和生物活性进行表征。结果表明,氧化锌阵列上细胞形态呈圆形,无铺展现象。而经聚乳酸修饰过的材料表面MC3T3细胞外基质铺展较好,细胞分泌的丝状伪足嵌入了阵列结构的空隙中,并且表面细胞数量最多,细胞活性明显高于氧化锌纳米棒及纯钛片。结果表明,聚乳酸涂层提高了氧化锌阵列的生物相容性,为细胞生长提供适宜的微环境,有效促进了细胞的黏附与增殖。     

超重力反应沉淀法制备氧化锰八面体分子筛

采用氧化还原沉淀法在超重力反应器中制备出氧化锰八面体分子筛(OMS-2),考察了加入的酸量、反应器转速、反应温度对OMS-2晶型和尺寸的影响。研究结果表明,超重力反应器中,当加入硝酸浓度达到2.32mol/L,反应器转速增大到1 200 r/min时才能获得晶型良好的OMS-2产品。而且改变转速对OMS-2晶体的尺寸和形貌无明显调控作用,温度对OMS-2的晶体尺寸有明显影响。反应温度60℃比30℃对应产物沿直径的横向生长速率更快,生成纳米棒直径增大。DSC和H2-TPR分析表明,超重力反应沉淀法相比于普通回流法制备出的OMS-2产物,其在550℃以下可在不破坏晶体结构的前提下更稳定持续地释放出体相氧物种。超重力反应沉淀法以水为溶剂,为实现氧化锰八面体分子筛的规模化清洁制备做出了有益的探索。     

CdS量子点/CdTe纳米棒光电极制备及其光电性能研究

本文利用化学沉积法和射频溅射法成功实现了CdS量子点/CdTe纳米棒复合光电极的制备。通过X射线粉末衍射(XRD)、扫描电镜(SEM)、紫外-可见吸收光谱(UV-vis)和电化学工作站分别对获得的光电极进行了结构、形貌和光电性能的表征;结果表明,所获得的光电极由CdS量子点和CdTe一维纳米棒组成,其中CdTe纳米棒沿着(111)择优方向定向生长。在不同CdS量子点厚度的光电极的电化学表征结果中,我们发现了由CdS的压电效应引起的新颖的热释电现象,并在25 cycle CdS QDs的光电极测试中获得了最好的结果,开路电压为0.49 V,短路电流为71.09 μA,其I-t曲线的开光比为6。我们在研究过程中还发现了热释电引起的电流反向现象,这一特性对于未来提高光电器件的性能具有重要的意义。     

多元醇法制备银纳米棒的放大试验影响因素研究

采用银晶种为引导剂,以高浓度硝酸银溶液为银源,乙二醇为还原剂,聚乙烯吡咯烷酮为盖帽剂,大规模制备银纳米棒。用扫描电镜,元素分析和X射线衍射对银纳米棒进行表征。结果表明,通过预加银晶种的方式替代添加金属盐类,最佳的反应条件为:搅拌速度为350 r/min,反应温度为160℃,硝酸银浓度不高于0.50 mol/L,采取体积放大6倍高浓度硝酸银制备银纳米棒时,需要提高银晶种的浓度为9.81 mmol/L,PVP/AgNO3摩尔比为1.3,该方法利用银晶种的引导作用,调控硝酸银的还原速度使之与银纳米棒的生长速度相匹配。     

Carbon nanorod supported metal alloy nanocubes using polydopamine as location reagent for water splitting

Transition metal catalysts were supposed to be the most likely substitute for commercial noble metal catalysts, and the development of highly active and long-term catalyst for water splitting are the future trend. Herein, Ni rectangular nitrogen doped carbon nanorods@Fe–Co nanocubes (Ni-CNRs@Fe–Co cubes) were fabricated via a facile template-free method. This simple strategy not only realizes the structure tailoring, but also achieves high-quality nitrogen-doping. Specifically, nickel dimethylglyoxime [Ni(dmg)₂] with rectangular rodlike structure was firstly synthesized by solution method, then metal-organic frameworks Fe–Co nanocube with different contents were loaded on rectangular carbon nanorods with polydopamine as the locating and the connecting agent, and finally Ni-CNRs@xFe-Co cubes were obtained by a one-step calcination. A series of electrochemical tests were researched on materials with different metal contents in the 1 M KOH solution. The Ni-CNRs@Fe–Co cubes show excellent electrocatalytic activity in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). For HER and OER, the Tafel slopes were 83.3 mV dec⁻¹ and 71 mV dec⁻¹, the onset potential were −167 mV and 1.62 V, and reached the current densities of 10 mA cm⁻², the overpotential just needed 196 mV and 433 mV, respectively. This novel synthetic strategy will provide a template-free way for cheap electrocatalysts of non-precious metal for OER and HER.     

Core-shell structure of polypyrrole grown on W18O49 nanorods for high performance gas sensor operating at room temperature

In this work, uniform core-shell structure of polypyrrole wrapped on tungsten oxide nanorods (PPy@W₁₈O₄₉ core-shell nanorods) were synthesized via a two-step process for gas-sensing applications. The core-nanorods of W₁₈O₄₉ were first grown by solvothermal method with tungsten hexachloride (WCl₆) as precursor. The PPy-shell layer was then formed uniformly on the solvothermally synthesized W₁₈O₄₉ nanorods by in-situ chemical polymerization of pyrrole monomer (Py), with sodium dodecyl benzene sulfonic acid (DBSA) as dopant and ammonium persulfate (APS) as oxidant. High dispersion of Py achieving in ethanol is proved to be crucial to form the uniform PPy-shell layer, and the layer thickness of PPy-shell is highly controlled by adjusting the Py concentration in polymeric solution. The morphology and structure of the nanocomposite were characterized systematically; it shows that the composite exhibits perfect core-shell structure of one-dimensional (1D) nanorods with average diameter of around 70–90 nm. The NH₃-sensing properties of the sensors based on the PPy@W₁₈O₄₉ core-shell nanorods were investigated at operating temperature of 15–130 °C over NH₃ concentration ranging from 1 to 200 ppm. The response magnitude of the PPy@W₁₈O₄₉ sensor can be affected seriously by temperature fluctuation, even in room temperature range (15–30 °C), and meanwhile, a temperature-dependent p-n response characteristic reversal is observed for the heteronanorods sensor. At much low room temperature of 15 °C, the present PPy@W₁₈O₄₉ nanorods show quick and sensitive response to NH₃ gas mainly due to the ultrathin, uniform PPy shell and the special heterojunction effect between p-type PPy and n-type W₁₈O₄₉. The underlying gas-sensing mechanism is analyzed.     

Supercritical hydrothermal synthesis of titanium dioxide nanostructures with controlled phase and morphology

A novel template- and organic-free synthesis of TiO₂ nanostructures with controlled phase and morphology was realized through batch supercritical hydrothermal treatment (400 °C) of titanate nanotubes (TNTs) with H₂O₂ in NaOH aqueous solution. Well-defined 3D titanate hierarchical spheres (THSs), 2D multilayered titanate nanosheets (TNSs), and 1D monodisperse anatase nanorods (ANRs) exposing (0 1 0) facets were prepared in 15 min by slightly varying the NaOH solution pH. Specifically, the obtained Na/H-THSs (without/with HCl neutralization) exhibited highly porous structures with large specific surface area (109 m² g⁻¹ and 196 m² g⁻¹, respectively). Temperature-dependent phase and morphology evolutions of products under subcritical condition (200 and 300 °C) were investigated. The formation of the TiO₂ nanostructures from TNTs was proposed mainly following a dissolution–nucleation-growth mechanism, suggesting that both supercritical temperature and NaOH solution pH were determinant factors governing the nucleation and growth process and thus the phase and morphology.